The present invention relates to the control of a storage system, and more particularly to the control of a remote copy process in a storage system that includes multiple storage subsystems.
In a storage system, remote copying is generally used in order to increase the reliability of data. Remote copying involves setting up a primary storage subsystem and a secondary storage subsystem within the storage system, and copying data written to the storage area of the primary storage subsystem to the storage area of the secondary storage subsystem.
Furthermore, in order to increase the reliability of data in the storage system, data stored in one primary storage subsystem is remotely copied to two or more secondary storage subsystems (this is also referred to as ‘multi-target remote copying’ below). In this type of storage system, it is necessary to ensure that the duplicate data stored in the two secondary storage subsystems is identical in the event some sort of error or problem occurs in the primary storage system, for example.
For example, a technology is known in which, in a storage system that includes a primary storage subsystem, a secondary storage subsystem in which duplicate data is written synchronously with the writing of data to the primary storage subsystem, and a different secondary storage subsystem to which duplicate data is written asynchronously with the writing of data to the primary storage subsystem, the sameness of the data residing in the two secondary storage subsystems is ensured simply by copying difference data regarding the differences between the two sets of data residing therein.
According to the conventional art described above, in the event of a failure in the primary storage subsystem, a copy pair can be quickly formed using the two secondary storage subsystems.